(a) Field of the Invention
The present invention relates to a novel pyran derivative, its preparation method, a liquid crystal composition and a liquid crystal display device comprising the same.
(b) Description of the Related Art
Liquid crystal compounds are widely used for various liquid crystal display devices applied for a watch, a notebook computer, a mobile phone, television and a monitor, etc., and demands therefor rapidly increase every year. Liquid crystal compounds used for the liquid crystal display devices include nematic liquid crystal phase, smectic liquid crystal phase and cholesteric liquid crystal phase, and nematic liquid crystal phase is most widely used. And, rather than using a single liquid crystal compound, various liquid crystal compounds are used in combination to satisfy physical properties required for various liquid crystal display devices.
More specifically, a liquid crystal composition comprising liquid crystal compounds should be stable to moisture, light, heat, air and electric fields, and chemically stable with each other under used environment, and it should have excellent compatibility with other liquid crystal compounds.
And, in order to be applied for a liquid crystal display device, a liquid crystal compound should have balanced physical properties of wide liquid crystal phase temperature range, appropriate refractive anisotropy (Δn) and dielectric anisotropy (Δ∈), viscosity and conductivity, etc. And, since required physical properties vary depending on the kinds of liquid crystal display devices, novel liquid crystal compounds that can be well mixed with various liquid crystal compounds to satisfy various physical properties depending on liquid crystal display device are continuously demanded.